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Commit 29bd3bc1 authored by Olivier Sobrie's avatar Olivier Sobrie Committed by David S. Miller
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hso: fix crash when device disappears while serial port is open 



When the device disappear, the function hso_disconnect() is called to
perform cleanup. In the cleanup function, hso_free_interface() calls
tty_port_tty_hangup() in view of scheduling a work to hang up the tty if
needed. If the port was not open then hso_serial_ref_free() is called
directly to cleanup everything. Otherwise, hso_serial_ref_free() is called
when the last fd associated to the port is closed.

For each open port, tty_release() will call the close method,
hso_serial_close(), which drops the last kref and call
hso_serial_ref_free() which unregisters, destroys the tty port
and finally frees the structure in which the tty_port structure
is included. Later, in tty_release(), more precisely when release_tty()
is called, the tty_port previously freed is accessed to cancel
the tty buf workqueue and it leads to a crash.

In view of avoiding this crash, we add a cleanup method that is called
at the end of the hangup process and we drop the last kref in this
function when all the ports have been closed, when tty_port is no
more needed and when it is safe to free the structure containing the
tty_port structure.

Signed-off-by: default avatarOlivier Sobrie <olivier@sobrie.be>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 3ac856c1

drivers/net/usb/hso.c

+13 −4
Original line number Diff line number Diff line
@@ -1270,7 +1270,6 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp) 
		goto err_out;



	D1("Opening %d", serial->minor);

	kref_get(&serial->parent->ref);



	/* setup */

	tty->driver_data = serial;
@@ -1289,7 +1288,8 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp) 
		if (result) {

			hso_stop_serial_device(serial->parent);

			serial->port.count--;

			kref_put(&serial->parent->ref, hso_serial_ref_free);

		} else {

			kref_get(&serial->parent->ref);

		}

	} else {

		D1("Port was already open");
@@ -1339,8 +1339,6 @@ static void hso_serial_close(struct tty_struct *tty, struct file *filp) 
		usb_autopm_put_interface(serial->parent->interface);



	mutex_unlock(&serial->parent->mutex);



	kref_put(&serial->parent->ref, hso_serial_ref_free);

}



/* close the requested serial port */
@@ -1391,6 +1389,16 @@ static int hso_serial_write_room(struct tty_struct *tty) 
	return room;

}



static void hso_serial_cleanup(struct tty_struct *tty)

{

	struct hso_serial *serial = tty->driver_data;



	if (!serial)

		return;



	kref_put(&serial->parent->ref, hso_serial_ref_free);

}



/* setup the term */

static void hso_serial_set_termios(struct tty_struct *tty, struct ktermios *old)

{
@@ -3214,6 +3222,7 @@ static const struct tty_operations hso_serial_ops = { 
	.close = hso_serial_close,

	.write = hso_serial_write,

	.write_room = hso_serial_write_room,

	.cleanup = hso_serial_cleanup,

	.ioctl = hso_serial_ioctl,

	.set_termios = hso_serial_set_termios,

	.chars_in_buffer = hso_serial_chars_in_buffer,